The present embodiments are directed to a magnesium-air battery.
Lithium (Li) ion technology has dominated the market as an energy source for small electronic devices and even hybrid and electric vehicles. However, current Li-ion batteries have insufficient energy density to be an energy source for future high energy density storage sources capable of running an electric vehicle.
Metal-air batteries have been under investigation as an advanced generation of high energy density sources which have the theoretical capability to power electronic devices and vehicles for distances comparable to present hydrocarbon based combustion engines. In a metal-air battery, the metal of the anode is oxidized and the resulting cation travels to the cathode zone containing a porous matrix of a material such as carbon, for example, where oxygen is reduced and the reduction product combines with the metal cation to form the discharge product as an oxide or peroxide. Upon charge, this process is ideally reversed. Metal-air batteries are recognized to have potential advantageous properties over metal ion batteries because the cathodic material, oxygen, may be obtained from the environmental air atmosphere and the capacity of the battery would in theory be limited by the anodic metal supply. Thus, oxygen gas or a form of ambient air would be supplied continuously from outside the battery and battery capacity and voltage would be dependent upon the oxygen reducing properties and chemical nature of the discharge product formed.
Metal-air batteries based on lithium, sodium and potassium are under investigation. For example, lithium air batteries have the potential to supply 5-10 times greater energy density than conventional lithium ion batteries and have attracted much interest and development attention as a post lithium ion battery technology. A nonaqueous lithium air battery which forms Li2O2 as discharge product theoretically would provide 3038 Wh/kg in comparison to 600 Wh/kg for a lithium ion battery having a cathodic product of Li0.5CoO2. However, in practice, the metal air technology and specifically current nonaqueous lithium air batteries suffer from many technical problems which have hindered achievement of the theoretical capacity.
Battery systems based on multivalent metals such as the alkaline earth metals theoretically have energy densities comparable to lithium, sodium or potassium. Of the alkaline earth metals, magnesium is of great interest because of its low cost, better handling properties and lower toxicity. Importantly, magnesium as an anode material is not known to form metal dendrites such as those known to form with lithium anodes. Aqueous primary batteries based on magnesium have been demonstrated, but the presence of the aqueous system limits the achievable cell potential and moreover, corrosion of the magnesium by water would have to be prevented in order to possibly prepare a rechargeable aqueous magnesium-air battery.
Non-aqueous magnesium-air battery systems would avoid the aqueous corrosion problem and offer the potential to provide a secondary (rechargeable) magnesium-air battery.
Thus, there is a need to provide nonaqueous magnesium-air battery systems and especially a magnesium-air battery system that is rechargeable. Such batteries may be useful as efficient, safe, cost effective, high energy density systems especially for powering vehicles to distances at least equal to or competitive with current hydrocarbon fuel systems.